Christopher Hitchens’ final posthumous memoir, originally scheduled to release in April, has been pushed back to a later date to allow for “simultaneous publication” in the U.S., U.K., and Australia.

Titled Mortality, the new book is expected to be about the late atheist’s battle with esophageal cancer, chronicled in a series of columns he wrote for Vanity Fair during the time of his illness.

Karen Duffy, the publicist for Atlantic Books, said that the move to September was initiated in the U.S. and would ensure that any additional information and material needed for the memoir in the wake of his death would be secured in the last book, including a new introduction, according to Benedicte Page.

Hitchens passed away mid-December at the age of 62 due to complications resulting from his stage IV esophageal cancer.

In his last essay written before his death, the renowned author reviewed a familiar maxim –“Whatever doesn’t kill me makes me stronger” – finding the principle less and less convincing as his health rapidly declined from the myriad of treatments he underwent, including radiation and a therapy co-created by evangelical scientist Francis Collins.

“Before I was diagnosed with esophageal cancer a year and a half ago, I rather jauntily told the readers of my memoirs that when faced with extinction I wanted to be fully conscious and awake, in order to ‘do’ death in the active and not the passive sense,” he penned.

“And I do, still try to nurture that little flame of curiosity and defiance: willing to play out the string to the end and wishing to be spared nothing that properly belongs to a life span.”

“However,” Hitchens added, “one thing that grave illness does is to make you examine familiar principles and seemingly reliable sayings. And there’s one that I find I am not saying with quite the same conviction as I once used to: in particular, I have slightly stopped issuing the announcement that ‘Whatever doesn’t kill me makes me stronger.’”

“In the brute physical world, and the one encompassed by medicine, there are all too many things that could kill you, don’t kill you, and then leave you considerably weaker,” he penned.

Writing several more pieces on his “deadly new enemy,” Hitchens’ columns on cancer eventually won him the National Magazine Award for Columns and Commentary in May 2011.

The latest memoir based on his award-winning essays had been planned for some time.

Atlantic Books (U.K.) and TWELVE Publishers (U.S.) also published Hitchens’ bestseller God is Not Great, Hitch-22, and his comprehensive essay collection Arguably.

Toby Mundy, chief executive of Atlantic Books, told The Guardian UK it was an honor to have published Hitchens’ books for the last seven years.

“There is no one like Christopher Hitchens. He was the most brilliant and versatile non-fiction writer of modern times, whose prodigious output was of stunning high quality, a showcase for his vast range, deep knowledge and fierce wit. When he was diagnosed with cancer, he faced it with characteristic honesty, courage and rigor. He is quite simply, irreplaceable.”

When asked about more details of the upcoming memoir, including who was chosen to write the new introduction, TWELVE Publishers did not immediately respond to The Christian Post.

Hitchens' brother, Peter Hitchens, recently announced on his blog that a memorial gathering for Hitchens would take place in New York City sometime during the spring, most likely in April, in place of a funeral since the late atheist's body was donated to science.

Another additional event would also probably take place in London, he shared. Details would be provided at a later date.